1 Field of the Invention
The present invention relates to a safety restraint system for workpersons on elevated ledges, e.g., on high rise buildings. The system comprises a safety cable extending between spaced cable supports along the elevated work space, and a lanyard slidably connected to the cable. The lanyard is attached to the worker to enable the worker safely to move along the elevated work space without danger of falling.
2. Prior Developments
The present invention addresses the safety problems of workers working on narrow ledges and the like, typically on high rise buildings. Such workers typically engage in such tasks as window washing, caulking, etc.
Conventionally, the safety restraint system comprises a wire rope or cable secured to posts or stanchions at spaced points along the length of a ledge or work space. Typically, the posts are spaced apart about seven to ten feet. Each worker has one or two lanyards (short-flexible safety lines) attached to his belt or body harness. The other free end of each lanyard has a snap hook adapted to fit onto the cable so as to be slidable along the cable to prevent the worker from falling while at the same time enabling the worker to walk back and forth along the elevated work surface, typically a ledge on the side of a high rise building.
When only one lanyard is used, the worker must detach the snap hook from the cable in order to transit, the hook across each cable support post. If two lanyards are used, the worker can maintain one lanyard attached to the cable while disconnecting the other lanyard from the cable and reattaching it thereto on the other side of the post. When only one lanyard is used, substantial hazard is involved in the transitioning of a lanyard hook across each cable support. When two lanyards are used, there is a potential danger if a worker inadvertently disconnects both lanyards, rather than disconnecting and reconnecting the lanyard hooks in proper order.
The problem of safely transiting lanyard hook across a cable support has been addressed in several patents. In some cases the solution has been to modify the cable support to have a separable connection with the cable. The hook or ring structure on the lanyard can then be slid along the cable by temporarily deflecting the cable away from the cable support. This solution is not, entirely satisfactory in that the cable is not rigidly supported, and can sway or float vertically to some extent.
In one prior device, the lanyard connector was constructed with a helical slot extending therealong, such that the connector can be passed across the cable support by simultaneously rotating and sliding the connector so that the slot passes over the post.
The devices of the patents discussed below are believed to be representative of the art.
U.S. Pat. No. 4,037,824 to Whitmer discloses a safety device wherein an elongated safety line cable passes through two arcuate horns spaced a slight distance apart at the upper end of a support post. A lanyard or fitting controlled by the workman fits about the cable and can be passed across the two arcuate horns without detaching the lanyard from the cable by rotating the lanyard back and forth about the cable axis in a helical motion about the two horns. One problem is that the two arcuate horns do not directly contact the cable, and the cable can swing or sway transversely, because it is not rigidly supported from the arcuate horns. The horns merely limit the swaying motion without preventing such motion.
U.S. Pat. No. 4,699,245 to R. Benedet discloses a workman safety device wherein a horizontal cable extends through a confined space between a vertical C-shaped yoke and a rotatable disk. A workman's harness has an attachment ring that encircles the cable. The ring is movable along the cable and into a notch in the edge of the disk. Continued movement of the ring along the cable causes the disk to rotate about the disk axis located below the cable. The ring can thus be moved within the notch and along the cable through the space circumscribed by the disk. One problem with the system is that the cable must be lifted from its normal position in order to accommodate arcuate motion of the notch in the disk. Depending on the weight and tension on the cable, some manual pulling effort is required. Another disadvantage is that the cable is not rigidly connected to the disk or to the C-shaped yoke, the cable merely passing through the yoke-disk space, so that the cable can sway to some extent.
U.S. Pat. No. 4,790,410 to Sharp, et al., discloses a safety apparatus that includes a safety cable extending through a tubular head carried by a fixed support arm. The workman's harness or line is connected to an arcuate yoke element that partially encircles an elongated tube. The elongated tube has a helical slot extending along its entire length so that when the tube is passed along the cable and over the tubular head, the helical slot will have a cam action on the fixed support arm, thereby rotating the elongated tube around its axis. The tube is rotatably mounted in the arcuate yoke element to be rotatable without necessarily causing the yoke element to rotate. However, the slotted tube is relatively long in order to achieve only limited small slot angulation. The cam action between the slot and the fixed arm occurs at points remote or offset From the arcuate yoke element, so that in practice some binding can occur between the slotted tube and the yoke element, thereby adding to operational difficulty. Also, over time the yoke surface will frictionally wear and possibly cause the yoke element to separate from the slotted tube.
U.S. Pat. No. 5,105,907 to Lebow shows essentially the same construction and operational mode as the Whitmer patent. However, in the Lebow arrangement the C-shaped cable guide elements are spaced relatively far apart, and a notched cable-support plate is located between the two C-shaped guide elements.
U.S. Pat. No. 4,721,182 to Brinkman, et al., shows an overhead guide rail suspended near the roof of an underground sewer duct. A travelling connector at the end of a lanyard encircles the rail to prevent a workman from being swept along the duct. The travelling connector has an openable gate or hook for operation by the workman to permit passage of the connector past a guide rail support member. During the period when the gate (hook) is in an opened condition, the workman must physically support the weight of the overhead connector.